Deconstructing the Fox drama House from A to Z is like solving the medical mysteries the hit series is famous for: You don’t know quite where to begin, and you’ll be surprised by where you end up. For example: Should A stand for atrophy, referring to the rotting muscle in Dr. Gregory House’s right leg? Or for ass, referring to the gimpy genius’ unapologetically prickly personality? ”Actually, I think A should stand for my ass,” says costar Lisa Edelstein (who plays his boss, Dr. Cuddy), alluding to House’s horndoggy fixation with her derriere. Torn, we left it to House himself to settle the matter: ”I think A should stand for appropriate,” says star Hugh Laurie. ”Let that thought guide you.”

We ultimately didn’t follow the doctor’s orders — even though they’re coming from one of the most compelling characters in TV history. For those familiar with the fearsome physician, consider this an insider’s guide with insight from Laurie, Edelstein, and creator David Shore; for the few who aren’t, consider it an introduction. Everything from killer microbes to killer sex is covered, although one answer you won’t find is a definitive diagnosis of House himself. Victim or victimizer? Redeemable or unsalvageable? Laurie hopes such questions are never answered. ”So much drama is overexplained, and House has thrived by avoiding the pat and the transparent,” he says. ”I don’t know myself most of the time what’s going on inside people’s heads — and I’m not sure I want to know.”

AADDICTIONHouse creator Shore modeled his flawed genius in part on Sherlock Holmes (they even have the same house address: 221B); ergo, House’s Vicodin dependency is a nod to the great detective’s cocaine habit.

CCOLLEAGUESIf House is Holmes, these are his Watsons. Lisa Cuddy is the long-suffering boss, while oncologist James Wilson (Robert Sean Leonard) is the long-suffering ”best friend.” Then there are the three doctors serving fellowships under him: Eric Foreman (Omar Epps), more like House than he wants to admit; the smitten Allison Cameron (Jennifer Morrison); and Robert Chase (Jesse Spencer), desperate for House’s affirmation.

DDIFFERENTIAL DIAGNOSISThe term for House’s claim to fame — cracking medical puzzles other docs can’t solve. Shore’s true confession: ”To my knowledge, there is no such thing as a ‘differential diagnosis’ department.” House’s tense rapport with his DD team has grown even more strained after he faked having brain cancer (in order to score an experimental painkiller). ”He’s on his ninth life with them,” says Laurie.

E”EVERYBODY LIES”House’s mantra, based on his cynical yet usually accurate assumption that patients are always hiding something. Like the case of the lady with African sleeping sickness who swore she’d never been to Africa…while neglecting to mention she was cheating on her husband with someone who had been there.

FFATHER ISSUESChase’s late dad was a famous physician who abandoned him as a child. Foreman’s deeply religious pop is disappointed by his son’s lack of faith. And House’s father was a demented disciplinarian who made him bathe in ice if he misbehaved.